Hyperactive boys are being treated with up to 15 mg/day of clorgyline, parnate or deprenyl (10 mg/day), selective and non-selective Monoamine Oxidase Inhibitors, or amphetamine (0.5/mg/kg). Behavioral measures include motor activity, vigilance and parent and teacher behavior ratings. Biological measures include urinary catecholamines and metabolites, urinary PEA and platelet MAO. The aim of the study is to elucidate neurotransmitter mechanisms mediating stimulant drug efficacy in hyperactivity.